The present invention is related to magnetic resonance (MR) magnet cartridges which includes the magnet coils and support that position the coils relative to one another.
Superconducting coils in an MR magnet are typically supported by a cylindrical shell which also serves as a winding form or by rings shrunk on the outside surface of freestanding coils which are joined to one another by axial struts. When a cylindrical shell serves as a winding form, the entire cartridge including all the coils is epoxy impregnated at the same time. A defective coil is not easily repaired and can cause the entire cartridge to be scrapped. When individual coils with shrunk on rings are assembled, achieving precise alignment of the coils relative to one another can be difficult, any misalignment adversely affects the magnetic field homogeneity which can be achieved by the magnet.
In refrigerated magnets, the support structure between the coils also serves to carry heat away from the coils to the cryocooler. The more support structure provided to improve heat conduction, the greater the weight of the magnet cartridge and the larger the suspension needed to support the magnet cartridge in the vacuum vessel, which adds to the heat load conducted through the suspension to the magnet cartridge.
It is an object of the present invention to provide a magnet cartridge with reduced weight and good heat transfer between coils.
It is a further object of the present invention to provide a magnet cartridge which permits precise alignment of the coils during fabrication.
It is a still object of the present invention to provide a magnet cartridge which permits cost effect replacement of a defective coil.